MiniM's Core XY project

Time for a buildthread for my CoreXY machine. I'm posting here since this is my first build and I need input on what stupid things I have designed that will not work so I can change them before building. Need all the help I can get so please post your thoughts

In short it's going to be built off these components:
-3030 Bosch Rexroth extrusions
-3030 Bosch Rexroth corner cubes
-2x MGN 15 500mm for the Y rails
-1X MGN 12 500mm for the X rail
-3X MGN 12 500mm for the Z axis
-3x 1204 ballscrews for the Z axis
-GT2 belt for the core xy mechanism
-3d printed parts but designed with CNC machininig in mind for all but the hotend mount.
-Guesstimated print area of approx 440x440x390mm
-5mm alu bed with 800W 230V bed
-2x NEMA17 steppers for core xy
-1x NeMA17 geared down for the Z axis joined by belt between the ballscrews
-Titan aero extruder
-Corner brackets to ensure rigid frame (not in CAD drawing)
-Duet Wifi eletronics
-Bed probing is undecided yet as I'm testing various setupts on my other printer (FSR or IR-sensor is the most likely choice)

The Z axis design is not complete yet as I think this will be very hard to align and there is a big chance of binding and overconstrain with fixed mounted ballscrews and linear rails on 3 spots. This is usual to do on CNC machines but aligning this in extrusions might be a nightmare. I didn't draw the supporting 3030 for the linear rail on the Z axis either but since I'm clueless on how to make the Z so it's very rigid I stopped at this.

I think two linear guides (sides) with three screws will do the job. I would use the linear guides as they are intended- bolted to flat plate or at least frame members. That will minimize Z wobble if the screws aren't perfect. I don't know what 3 ball screws and bearings and pulleys and hardware will cost, but it might be cheaper to use a belt lifted Z axis which won't create any lateral forces that can cause Z wobble. My printer has a 300x300 mm bed lifted on two linear guides by two belts. You might have to go to 3 belts to lift a 440 x440 bed. Details here.. There's one relatively expensive component- the 30:1 worm gear reducer/motor.

You don't need corner blocks for the frame. Bolt the members directly to each other. See: [www.instructables.com]

Thanks for your input. I think you are right there sir. Will try to sketch it up tonight and see how it looks. Ideally I think I should also mount the ballscrew and linear rail before it coes into the printer, that way I can align them with a micrometer towards eachother and when lining up the rest I only have to worry about 3 items beeing aligned instead of 5 items. Is there any good aproach to it? Regarding cost it's allready to late as all these parts is parts I got lying around. I'm only missing the 3030 extrusions but they are shipping with DHL as we speak. I actually read about a belt setup like yours recently and I kind regret I didn't go that way now. Much cheaper and simpler solution. It's not to late yet I guess but then I got 3 wasted 1204 ballscrews with all parts..

I got those corners for free since rs-components messed up my 3030 order delaying it with two weeks. Do you think that's a bad way to go? I really liked that I could design my machine to all use 590mm extrusions when I used them. This way I don't have to cut any extrusion in other length and I can use my cut jig all the way. I don't have access to a mill either so I'm not sure I'm able to get it 100% accurate cuts with my saw

Yay, the extrusions came today so I mounted my cutting jig and calibrated the saw as good as I could to cut in angle. It cut wood fine, but the extrusions came out of angle I mounted up one piece just to check the angle and it was decent so I decided to cut the rest and see if I could get it working.

Then I had to mount a frame and see how it was so I threaded all the ends with M8x1.25 threads and mounted it togheter. The result is horrible! Way out of angle due to my cutting. The lengt is ok but it's not 90 degrees cut. Do you guys think it will be possible to adjust it out as I mount the rest of the frame or should I start shimming at once? I ordered only 4 corner brackets so will have to place a order for more to continue.

I actually got some similar looking on order from Aliexpress. It's only been two weeks tho so will prolly be a while until I got them here. Will grab some more of those corner cubes as they where pretty neat. No clue what to do with the misalignment but I hope it might get better once I connect the rest of the frame. Maybe I can try to turn some of the extrusions also as it's the cut that is not in angle so i could trick it some that way maybe ^^

I think the best thing you could do now is hunt for someone who has a mill and get them to square up the ends of the frame pieces for you. Your cuts may be unsquare in two dimensions, so when you assemble a rectangle using the cubes and 4 of your cut pieces, there's no guarantee the rectangle will be both square and flat. You'll have to modify your design to accommodate the slightly shorter pieces- you'll probably lose 2-5mm or so from each piece, depending on how bad the saw blade alignment was. That shouldn't be too big a problem. Make sure that whoever does the work knows you want the pieces to be equal lengths, too. All that means is they'll have to put an block on the mill table when they do the final squaring. It's about a 2 minute setup on the machine and about a 15 minute job to square all the pieces and equalize the lengths.

Start asking friends and relatives about machinists, hunt for a local makerspace, or check your local university. Someone near you has a mill and will do the work in exchange for a 6 pack of beer (it'll be the easiest 6-pack they ever earned). The next time you build a printer, order the t-slot cut to length. I believe Misumi cuts accurately or mills things to length/square for a minimal additional charge.

The frame doesn't have to be absolutely square, but it will make aligning the guide rails parallel and square much easier if it is. With a square frame, you can use metal or wood spacers to position the ends of the rails equal distances from frame members. If the frame is square, the guide rails will be square/parallel. If the frame isn't square, I don't know how you'll get the guide rails into alignment.

You can check the frame for squareness by measuring diagonals on each side. If the frame is square, the diagonals will measure the same.

Knowing the difference between things you can do better yourself (building a 3D printer) and things you can't (cutting aluminum squarely) takes some experience. You just acquired some of that, so you'll know better next time. Anything that requires critical alignment requires precise cutting/drilling/assembly or has to be designed to be adjustable.

Just wish I didn't sell my Omio CNC 2200 a year ago Would have been so much simpler clamping down the extrusions and milling the ends than using a wiggly saw. Proper tools is 50% of the job and I lack that. I started asking around for someone to mill the ends of the extrusions now as you suggested.

Another option is to buy a new saw that is not wiggly or a cheap mill and redo it myself. Mastering it would be a lot better feeling than hiring someone to do the work for me..

Norway doesn't have many makerspaces outside the biggest cities and in my city it's only 3d printer/vinyl cutter listed as tools :/ But I'm member of a norwegian cnc group from when I had my cnc router so I'll try my luck there or at some local company. I realize that skipping the alignment part now will only make things harder then it needs to be when it comes to assembly and tuning of the machine later.

And still no word from the machine shop i received the missing corner brackets now so will try to drive around tomorrow and see if I can get anyone to do the milling for me. Hope it get solved somehow. If not I will buy a mill. I see they have it in stock in my local cnc shop.

Went to the machine shop today to get a price quote for milling of the ends. They qouted me $260 to mill them off to equal lenght. It was a stiff price tag for that work so I'm really considering getting a mill and doing it myself.. This is prolly not my last build and I would love one for machining the other parts like stepper mounts, idler mount, X carriege mount and so on. They stocked a machine called WMD16VA and a WMD25V. WMD25V is in the upper pricerange but it was like twice the size of the WMD16VA and looks way more sturdy. All these choices

Larger machine shops really don't want to do that kind of work and mark it up accordingly. Its risky to do business with hobbyists because sometimes they don't actually know what they need.
Everyone eventually runs into a clown who asks for a 1" shaft (no tolerance) and then refuses to pay because it doesn't fit the 25mm bearing. Its just too much potential headache for a job that might net $20 at regular shop rate.

Remember that tooling and accessories add up. Getting a mill usable might add another 50-100% of list price, and a more complete set of cutting tools, workholding, and metrology would probably set you back 200-400% of the mill price.

Yes I kinda knew that and it's the same in my line of work.. Impossible for them to make money on small stuff like this. It was worth a try tho since I could have a look at those machines when I was there.

I know this because I bought all that stuff recently when I got my CNC router.. I sold it not to long ago along with tooling and clamping tho so I'm back on scratch. Regret that bigtime now as it would have been no problem at all to mill the ends with that. He promised good prices on a machine vice and some endmills to get me started and he could throw in some decent mills he didn't use anymore. Will see what the total adds up to but If I can get a machine and some tooling/clamping to get me started for around $2500 I'd rather pay that instead of throwing $260 into this and next time around when I need some work it's another $260 and so on. Would be awesome to make the other parts in aluminium aswell instead of 3d printed parts.

Still searching for private persons that could help but it doesn't look like it's going to happen

Some photos from today. I tried mounting the frame and it goes fine together but it's way out of alignment as mentioned. Also tried loosing the corners and using brackets aligning them manually. Could MAYBE work if I loosened it even more on the corner cubes but it's hard to keep track of the lengths when "cheating" it together like that. Last run before I gave up it was 1mm out on 590mm lenght. Way to much for a precisssion machine..

Today the parts went to a school that takes the end milling for me as a school project in a mill. I will get a square frame and the money goes straight to the class account so for a good purpose. Win win Really looking forward to start building this beast now.

Not much is happening due to many other projects but I've finalized the design on the Z axis and started mounting it on the machine. The ballscrews and linear rails are mounted and lined up. I designed a little tool for aligning MGN12 rails to 3030 extrusions. I've seen similar designs so the idea isn't mine ^^

I've been battling if I should do a 3 stepper setup with true bed leveling on the Duet wifi or belt and one stepper to drive it all. Today I decided that I will do the 3x stepper setup and test the bed leveling. I will do some testing before ordering a Deux5 board to have enough stepper channels but others say that it work fine. It's tempting to never have to touch the leveling screws either for manual leveling. This is the first design of the Z stepper motor holders. I ran out of T slot nuts so I had to order new ones from China and wait a few weeks before I can continue the build :/